Hi,
Welcome to the ehealthforum and I am glad to help you out. When pregnancy occurs, cessation of menses occurs. Since you had your periods, so chances of pregnancy are less and these look like irregular periods. High level of stress, cholesterol, hormonal imbalance, chain smoking, dramatic changes in your life style may be some of the common causes of you irregular periods.
Other causes include medical conditions like PCOS and fibroid uterus. PCOS is diagnosed by blood tests like blood insulin levels, serum testosterone and androgen levels and ultrasound. Fibroids are benign tumors of the uterus. They are diagnosed by ultrasound lower abdomen or CT abdomen. If this was the first episode of irregularity in the periods, then wait for the coming cycle and try lifestyle modification by reducing stress and decreasing cholesterol levels. But if the repeat happens, then please consult a gynecologist and get yourself thoroughly examined to diagnose the cause of irregular periods and start with the treatment.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care.